WO2015087292A1

WO2015087292A1 - Method and facility for treating a liquid containing a suspension, in particular raw water, sludge, or urban or industrial effluents

Info

Publication number: WO2015087292A1
Application number: PCT/IB2014/066847
Authority: WO
Inventors: Jean-Michel FACCIOLI; Gauthier THOMAS
Original assignee: Degremont
Priority date: 2013-12-13
Filing date: 2014-12-12
Publication date: 2015-06-18
Also published as: FR3014864B1; EP3080051A1; FR3014864A1; ES2656297T3; EP3080051B1

Abstract

A method for treating a liquid containing a suspension, in particular raw water, sludge, or urban or industrial effluents, comprising a step of injection flocculation by injecting one or more conditioning products into the liquid to be treated at a rate of conditioning, in order to generate flocs for subsequent solid/liquid separation, which involves: estimating, by means of an industrial viewing system, the size of the flocs; categorising the flocs into two categories, i.e. large flocs and small flocs, with enumeration by category; estimating the ratio L/S of the number L of large flocs to the number S of small flocs; increasing the rate of conditioning, over time, from a settable low value; monitoring the variation (2) in the rate of conditioning and the ratio L/S (1) until a maximum (3) is reached for this ratio, and choosing, for the flocculation step, the rate of conditioning (4) corresponding to the maximum obtained for the ratio L/S.

Description

METHOD AND INSTALLATION FOR TREATING A LIQUID COMPRISING A SUSPENSION, IN PARTICULAR RAW WATER, SLUDGE, URBAN OR INDUSTRIAL EFFLUENTS.

The invention relates to a method for treating a liquid containing a suspension, in particular raw water, dilute sludge, urban or industrial effluents, comprising a flocculation step by injection of one or more conditioning products in the liquid to process, to generate flocs for subsequent solid / liquid separation. The method is applicable in all areas of the treatment of a suspension, resulting from the production of drinking water or the treatment of urban or industrial effluents, implementing a flocculation. The generic term flocculation encompasses the terms coagulation and / or flocculation relative to operations that use reagents of different natures but always to agglomerate particles suspended in the liquid.

Good flocculation of the slurry to be treated is critical to ensure the performance of the solid / liquid separation devices, such as settling, thickening, flotation, dehydration, or other effect, which are downstream of the flocculation step. It is therefore imperative to continuously determine the rate of conditioning, that is to say the dose of product (s) conditioning to be added to the suspension to be treated. The quantity of packaging product (s) added must be:

- necessary to obtain an optimal flocculation whatever the variations of loads, flows, concentration, in particular in Materials in Suspension (MES), and quality of the effluent to be treated, for example the ratio

Volatile matter / dry matter (MV / MS),

- just sufficient to avoid an overdose or underdosing disrupting the operation of the solid / liquid separation and equipment downstream, these under or overdosing can be a factor of economic loss A first current solution is to apply to the suspension, a conditioning rate determined in the laboratory. Sample collection and laboratory analysis should be done quickly so that the nature and quality of the effluent are not impaired. The rate of conditioning is often expressed by a mass ratio of product of conditioning and materials dry: for example in kg of dry matter product (kilograms of active ingredient / tonne of solids).

Another solution, as described in FR 2 971 782 in the name of the applicant company, is to use a machine vision system that continuously regulates the quality of flocculation. The system allows you to:

- characterize the size of the flocs,

- classify them by families of small flocks S (small) and large flocs L (large),

- estimate the S / L ratio,

- determine a limit value Q for this S / L ratio,

- regulate the quantity of product injected according to the S / L ratio: increase of the treatment rate when the S / L ratio is greater than the target value Q, decrease of the treatment rate when the S / L ratio is lower to the target value Q.

These solutions of the state of the art have several disadvantages, including the following.

In the case of a specific analysis in the laboratory, the transposition of the treatment rate is based on different hypotheses:

the nature and concentration of the conditioning products are constant over time,

- the quality of the suspension is constant over time

These assumptions are rarely verified and the treatment may be inappropriate.

In the case of FR 2 971 782, regulation is made difficult by the evolution of sludge quality. Indeed, the numbers of large flocs L and small flocs S are related to the nature and the quality of the effluent. Therefore, setting a limit resumes the assumption of having a constant effluent quality, this is rarely verified.

In addition, the system as described in FR 2 971 782 can generate noise of sufficient intensity to disturb the regulation.

One of the aims of the invention is to provide a quasi-universal and reliable solution of a liquid treatment containing a suspension which no longer has, or to a lesser degree, the disadvantages mentioned above. It is furthermore desirable that the treatment process be of such a moderate and relatively economical form. According to the invention, the process for treating a liquid containing a suspension of solids, in particular raw water, sludge, urban or industrial effluents, comprising a flocculation step by injection into the liquid to be treated of one or more products conditioning apparatus to generate flocs for subsequent solid / liquid separation, wherein:

it is estimated, by an industrial vision system, the size of the flocs,

the flocks are classified into two categories, namely large flocks and small flocks with enumeration by category,

the ratio L / S of the number L of large flocs to the number S of small flocs is estimated, is characterized in that:

the rate of conditioning is increased, as a function of time, from a parameterizable low value,

- the variation of the conditioning ratio and the L / S ratio are followed up to a maximum for this ratio,

and, for the flocculation step, the conditioning ratio corresponding to the maximum obtained for the L / S ratio is chosen.

The invention consists of determining periodically, or continuously, the optimum treatment rate to be applied to a suspension.

Advantageously, the rate of conditioning of the packaging product or products is continuously increased, in particular linearly, as a function of time. Alternatively, the rate of conditioning of the packaging product (s) may be increased discontinuously, particularly in steps, as a function of time.

When the liquid to be treated circulates in a pipe, the estimates can be made online, and the injection of conditioning product into the pipe is provided by a metering pump whose flow rate is controlled to ensure the increase of the treatment rate.

In the case of a liquid to be treated flowing in a main pipe, the variation of the conditioning ratio and of the L / S ratio until reaching a maximum for this ratio, and the estimation of the optimum rate can be carried out on a fraction. flow rate in a branch line, and the optimum conditioning rate is applied to the flow rate of the main line.

The duration of the increase in the rate of conditioning can be approximately 10 minutes. The determination of the maximum of the L / S ratio can be renewed periodically, in particular by period of 1 hour.

The machine vision system then operates according to the following steps: - characterization of the floc size,

classification of flocks by family of small flocs S and large flocks L,

- estimation of the L / S ratio,

determination of the optimum by increasing the treatment rate: the system progressively increments the treatment rate from a parameterizable low value. In parallel with this incrementation, the L / S ratio increases until the appearance of a maximum. The optimum is then at the maximum of the L / S ratio.

The invention also relates to an installation for treating a liquid containing a suspension, in particular raw water, sludge, urban or industrial effluents, for the implementation of the process as defined above, comprising:

liquid supply means to be treated,

an adjustable means of global injection of product (s) for packaging into the totality of the liquid to be treated,

a system of industrial vision capable of estimating the size of the flocs,

a calculator or programmable logic controller whose input is connected to an output of the machine vision system to receive the information on the flocs, and establish the ratio L / S of the number of large flocs to the number of small flocs, and control the means adjustable injection,

characterized in that

- said installation comprises a device for injecting test product (s) conditioning in all or fraction of the liquid to be treated,

- the computer is programmed to

- control the test injection device and increase, as a function of time, the injection rate and the conditioning rate from a parameterizable low value,

- follow the variation of the conditioning ratio and the L / S ratio until reaching a maximum for this report,

and applying to the global injection means, for the flocculation step, the level of conditioning corresponding to the maximum obtained for the L / S ratio. The installation may comprise a device for mixing the flocculant downstream of the test injection device and upstream of the machine vision system.

In the case where the liquid to be treated circulates in a pipe, the test injection device and the overall injection means may be combined and constituted by the same metering pump capable of injecting the conditioning product in the entire flow rate. of liquid flowing in the pipe, the machine vision system being installed on the same pipe. In the case where the liquid to be treated circulates in a main pipe, the installation may comprise a bypass line of the main pipe, and a unit comprising the test injection device, the machine vision system and the computer or programmable controller, is disposed on the bypass line, while the overall injection means is constituted by a metering pump, separate from the test injection device, suitable for injecting the conditioning product in the main pipe.

The invention consists, apart from the arrangements described above, in a certain number of other arrangements which will be more explicitly discussed hereinafter with regard to exemplary embodiments described with reference to the appended drawings, but which are not in no way limiting. On these drawings:

Fig. 1 is a diagram illustrating the treatment method according to the invention, and representing, as a function of the time taken on the abscissa, the variation of the conditioning rate carried on the ordinate axis on the right, and the variation of the L / S ratio brought on the y-axis on the left.

Fig. 2 is a schematic view of a treatment plant implementing the method of the invention, and

Fig. 3 is a schematic view of a variant of the treatment plant with a bypass line.

Referring to FIG. 1, the illustration of the determination of the optimum of the treatment rate can be seen. A curve 1 represents the evolution of the L / S ratio of the number of large flocs to the number of small flocs in the liquid to be treated, carried on the left axis of ordinates, after injection into this liquid of the conditioning product or products, according to a rate carried on the right axis of ordinates.

A curve 2 represents the incrementation, or increase, of the rate of conditioning as a function of time as abscissa. Curve 1 is rising up to a maximum of 3, representing the opti mum of flocculation. The optimum conditioning rate 4, associated with this maximum, corresponds to the point indicated on the right axis of ordinates.

After determining the optimum conditioning rate, it is applied to a treatment unit of the industrial treatment plant, possibly with a correction factor determined according to the type or processing technology used. on the industrial plant.

Fig. 2 schematically shows a treatment installation 5 according to the invention. The installation is fed by a pipe 6 in liquid containing a suspension of solids. A pump 7 disposed on the pipe 6 sets the liquid in motion. A supply of reagent (s) conditioning is performed by a pipe 8, which is installed on a metering pump 9. The reagent (s) is (are) then conveyed (s) by the pump 9, in order to their injection into the liquid of the pipe 6. The pump 9 is the device for injecting a flocculant into the liquid to be treated.

A mixer 10 is provided on the pipe 6 downstream of the pump 7. An inlet of the mixer 10 is connected to the outlet of the pump 7, another inlet of the mixer 10 is connected to the outlet of the pump 9. The flocculation is performed by the mixer 10 driven by a motor, and clean to provide the mixing energy necessary to perform the flocculation.

The liquid containing the conditioned suspension leaves the mixer via a pipe 11. A machine vision system 12 is disposed on the pipe 1 1, downstream of the mixer 10. Such a machine vision system 12 is available from equipment manufacturers and generally comprises a video camera scan to form digital images of the flocs generated in the liquid, and analysis means for estimating the size of the flocks, and preferably counting them.

The machine vision system 12 analyzes the quality of flocculation. It sends its analysis to a PLC 13 via the (the) connection (s) 14. The controller 13 records the analysis of the quality of flocculation, materialized by the ratio L / S (number of large flocs / number of small flocks), in parallel with the treatment rate fixed to the pump 9 by the connection 15. The size of the small flocs (the size being defined as the average size of the floc) can be between 0.2 and 0, 5 mm, and the size of the large flocs can be between 2.5 mm and 8.0 mm. Once the analysis is complete, the controller 13 returns the value of the optimum treatment rate via the connection 15 to the dosing pump 9 of reagent (s of treatment to adjust the rate to the optimum and via the connection (s) ( s) 16 to another unit not shown in Fig. 2, but constituted by a reagent pump 21 for a main line according to Fig. 3. The liquid outlet, with flocculated suspension and analyzed, is carried out via line 17, following the machine vision system 12.

In the case of Fig. 2, the pump 9 constitutes at the same time:

a flocculant test injection device whose injection rate is increased to determine the maximum of the L / S ratio and the optimum conditioning ratio,

and an adjustable means of overall injection of the optimum level of flocculant into the totality of the liquid to be treated.

In the case of FIG. 3, the pump 9 constitutes the flocculant test injection device for determining the optimum rate on a fraction derived from the liquid to be treated, while another pump 21 constitutes the adjustable means of overall injection of the optimum rate of flocculant. in the totality of the liquid to be treated.

According to the diagram of FIG. 2, the polymer conditioning ratio increases linearly from a low, non-zero value. The starting value could be zero in the absence of elements to determine a non-zero starting value. The duration of the incrementation to reach the maximum of the L / S ratio can be of the order of 10 minutes. The frequency of the measurements performed by the machine vision system can reach 40 seconds. The procedure for determining the maximum L / S ratio can be renewed periodically, especially every hour.

The speed of passage of the liquid, in particular of the sludge, in front of the camera of the machine vision system is advantageously between 0.1 and 0.5 meters / second. The present invention is based on the fact that the floc measurement is made under conditions identical to the packaging process.

The control of the flocculation state results from an instantaneous analysis of the digital representation of the flocculation, contrary to a control of physico-chemical parameters of the suspension: the uncertainties relating to the quality of the suspension are, in this case , deleted. Example of realization:

To allow the system to be installed on all types of installation (nature and flow of the suspension), the system can be placed in bypass of the main industrial conditioning pipe. In the context of a thickened organic sludge packaging, present on an urban wastewater treatment plant, the plant comprises a unit 5 '(FIG 3), similar to the installation 5 of FIG. 2, which is placed on a pipe 6 'bypassing a main pipe 18 of liquid subjected to packaging. The unit 5 'then determines the optimum treatment rate, in particular a ratio of flow rate: Q _{of reaotot} / m ³ Knowing the pumping rate of the effluent on a workshop and the operating range of the pump (s) ( s) metering (s) 21, the system corrects the flow rate of the metering pump (s) to apply the optimum treatment rate on the packaging line.

Fig. 3 illustrates this application. The elements of FIG. 3 identical or similar to elements already described above are designated by the same references, possibly followed by the sign of the apostrophe ', without their description is repeated, or recovery in detail.

The integration of the 5 'is observed in the packaging line. The feed line, conditioning thickened sludge is performed by a pipe 1 8. The sludge pump (s) 19 of the workshop carries (s) the sludge. The supply line 6 'of the unit 5' is branched to the main line 18. One 5 'has the pump 9 constituting the flocculant test injection device in the branch line 6' , to determine the maximum of the L / S ratio and the optimum packing rate um. The unit 5 'comprises the mixer 10, the controller 1 3 and the machine vision system 12, acting on the pipe 6', as shown for FIG. 2. The estimation of the floc size, the L / S ratio, and the conditioning ratio corresponding to the maximum obtained for the L / S ratio is performed on the flow in the branch line 6 '. The liquid of the pipe 6 ', after treatment, is discharged to a discharge 17'. Alternatively, the liquid of the pipe 6 'could be reintroduced upstream of the sludge treatment unit. A polymer solution tank 20 feeds bypass, the line 8 'going to the unit 5' for the reagent injection pump in the branch line 6 '. A metering pump (s) 21 of the packaging shop is (are) provided (s) to inject the (the) reagent (s) conditioning in the main pipe 18, downstream of the connection of the pipe 6 '. The pump 21 constitutes the adjustable means of overall injection into the entire liquid to be treated. In Fig. 3, the connection (s) 16 between the controller of the unit 5 'and the metering pump (s) 21 of the workshop is (are) highlighted (s) . It is through it (s) that the piloting operations of the pump 21 are carried out. The rate of reagent (s) injected by the pump 21 is set to the optimum value controlled by the unit 5 'and transmitted by the connection 16. Downstream, a dewatering system 22 is materialized. The implantation as described, ensures periodic or periodic automatic adjustment of the treatment rate. This implantation is easy to perform on an existing installation, especially with implementation of a derivation.

By way of nonlimiting example, for a flow rate of the order of 50m3 / hour in the main pipe 18, the flow rate in the bypass line 6 'can be 1 to 4m3 / hour, adapted to the possibilities of the vision system industrial. Circulation in the derived line occurs only during the duration of the measurements.

The following industrial applications can be mentioned:

• Urban effluent treatment

• Treatment of purification of industrial effluents

• Potabilization treatment of raw water

• Thickening or dewatering of wastewater from urban effluents

• Thickening or dewatering of effluent from industrial effluents

• Thickening or dewatering of sewage treatment effluents.

Claims

1. A method for treating a liquid containing a suspension, in particular raw water, sludge, urban or industrial effluents, comprising a flocculation step by injection into the liquid to be treated, one or more conditioning products according to a rate in order to generate flocs for subsequent solid / liquid separation, according to which:

it is estimated, by an industrial vision system (12), the size of the flocs,

the ratio L / S of the number L of large flocs to the number S of small flocs is estimated, characterized in that:

the variation (2) of the conditioning ratio and of the L / S ratio (1) is followed up to a maximum (3) for this ratio,

and the conditioning ratio (4) corresponding to the maximum obtained for the L / S ratio is chosen for the flocculation step.

2. Method according to claim 1, characterized in that the rate of conditioning of the conditioning product or products is increased continuously, particularly linearly, as a function of time.

3. Method according to claim 1, characterized in that it increases discontinuously, particularly in steps, as a function of time, the rate of conditioning of the packaging products.

4. Method according to any one of the preceding claims, for a liquid to be treated flowing in a pipe (6), characterized in that the estimates are made online, and the injection of packaging product into the pipe is provided by a metering pump (9) whose flow rate is controlled to ensure the increase of the treatment rate.

5. Method according to any one of claims 1 to 3, for a liquid to be treated flowing in a main pipe (18), characterized in that the variation of the conditioning ratio and the L / S ratio to a maximum for this ratio, and the estimation of the optimum rate are carried out on a fraction of the flow of the main pipe, in a branch pipe (6 '), and the rate of conditioning optimum is applied to the flow rate of the main pipe (18).

6. Method according to any one of the preceding claims, characterized in that the duration of the increase of the rate of conditioning is about 10 minutes.

7. Method according to any one of the preceding claims, characterized in that the determination of the maximum of the L / S ratio is renewed periodically, in particular by period of 1 hour.

8. Water or sludge treatment plant, for carrying out the method according to any one of the preceding claims, comprising:

supply means (7, 19) for liquid to be treated,

an adjustable means for global injection (9, 21) of product (s) for packaging in the totality of the liquid to be treated,

an industrial vision system (12) capable of estimating the size of the flocs,

a calculator or programmable logic controller (13) whose input is connected to an output of the machine vision system (12) to receive information on the flocs, and establish an L / S ratio of the number of large flocs to the number of small flocs, and controlling the adjustable injection means (9, 21),

characterized in that

- said installation comprises a test injection device (9) of product (s) conditioning in all or fraction of the liquid to be treated,

the computer (13) is programmed to

- control the test injection device (9) and increase, as a function of time, the injection flow rate and the conditioning rate from a parameterizable low value,

- follow the variation (2) of the conditioning ratio and the L / S ratio (1) until reaching a maximum (3) for this report,

and applying to the global injection means (9, 21), for the flocculation step, the conditioning ratio corresponding to the maximum obtained for the L / S ratio.

9. Installation according to claim 8, characterized in that it comprises a device (10) for mixing the flocculant downstream of the test injection device (9) and upstream of the machine vision system (12).

10. Installation according to claim 8 or 9, wherein the liquid to be treated circulates in a pipe (6), characterized in that the test injection device and the overall injection means are combined and constituted by the same metering pump (9) capable of injecting the conditioning product into the entire flow of liquid circulating in the pipe (6), the machine vision system (12) being installed on this same pipe (6, 1 1).

1 1. Installation according to claim 8 or 9, wherein the liquid to be treated circulates in a main pipe (18), characterized in that it comprises a bypass line (6 ') of the main pipe, a unit (5') comprising the test injection device, the machine vision system and the computer or programmable logic controller being arranged on the bypass line (6 '), while the global injection means is constituted by a metering pump (21) , distinct from the test injection device, suitable for injecting the conditioning product into the main pipe (18).